Behavior of allMatch, anyMatch and noneMatch for empty Stream

[Vitaly Davidovich]

Hmm, that's a different semantic though - the caller is passing an instance
of a predicate, not a predicate that throws NPE if invoked.

As it stands now, the behavior is inconsistent, possibly confusing at
runtime, and unintuitive, IMHO.  FWIW, .NET's analog explicitly checks for
null (and throws) input before iterating.

Sent from my phone
On Dec 12, 2012 10:44 AM, "Olexandr Demura" <oleksander.demura at gmail.com>
wrote:

> By some unknown reason I percept null to be effectively equal to any
> chosen SAM with method defined to throw NPE.
> e.g. Streams.emptyStream().anyMatch(o -> ((Boolean) null).booleanValue())
>
> 2012/12/12 Vitaly Davidovich <vitalyd at gmail.com>
>
>> Brian,
>>
>> I think NPE should be thrown when predicate is null irrespective of stream
>> length for consistency sake.
>>
>> Thanks
>>
>> Sent from my phone
>> On Dec 12, 2012 9:16 AM, "Brian Goetz" <brian.goetz at oracle.com> wrote:
>>
>> > These values are correct.
>> >
>> > All/None match correspond to universal quantification, which can be
>> > vacuously satisfied; Any match corresponds to existential
>> > quantification, which cannot.
>> >
>> > On 12/12/2012 6:26 AM, elena votchennikova wrote:
>> > > Hi,
>> > >
>> > > please clarify behavior of allMatch(Predicate), anyMatch(Predicate)
>> and
>> > > noneMatch(Predicate) methods for empty Stream.
>> > >
>> > > 1) Please look at the next code:
>> > > System.out.println(Streams.emptyStream().allMatch(o -> true));
>> > > System.out.println(Streams.emptyStream().anyMatch(o -> true));
>> > > System.out.println(Streams.emptyStream().noneMatch(o -> true));
>> > >
>> > > The result output will be:
>> > > true
>> > > false
>> > > true
>> > >
>> > >
>> > > Is it OK? And will such behavior be specified?
>> > >
>> > > 2) Methods allMatch, anyMatch and noneMatch throw NullPointerException
>> > > if Predicate is null, for example:
>> > > Stream notEmptyStream = Arrays.stream(new Object[] {new Object()});
>> > > notEmptyStream.allMatch(null);
>> > >
>> > > But if Stream is empty methods will not throw NPE.
>> > > So, next code will print same result as in point 1)
>> > > System.out.println(Streams.emptyStream().allMatch(null));
>> > > System.out.println(Streams.emptyStream().anyMatch(null));
>> > > System.out.println(Streams.emptyStream().noneMatch(null));
>> > >
>>  > > Is it OK or calling these methods with null-Predicate should throws
>> NPE?
>>
>